Liquid crystal display devices can be driven at low voltages with low electric power, and as such, have recently been employed as thin and light flat-panel displays in a broad range of commercially available products. Known as such a liquid crystal display device is a matrix liquid crystal display device.
The matrix liquid crystal display device, which has pixels arranged in a matrix manner, displays an image, a character, or the like, by applying a drive voltage independently to each of the pixels and thereby causing a change in optical characteristic of liquid crystals. Among such matrix liquid crystal display devices, an active matrix liquid crystal display device is capable of displaying a high quality image with characteristics such as a high contrast and a high response speed because the active matrix liquid crystal display device has a switching element such as a TFT (Thin Film Transistors) or MIM (Metal Insulator Metal) provided in each pixel.
As for such an active matrix liquid crystal display device, there has been proposed a structure, intended to improve an aperture ratio of pixel electrodes, in which (i) the pixel electrodes are provided on an interlayer insulating film and (ii) the pixel electrodes are provided on a layer different from a layer on which the respective signal wires are provided. This causes each of the pixel electrodes and a corresponding one of the signal wires to overlap each other (e.g., see Patent Literature 1).
However, an active matrix liquid crystal display device structured as mentioned above causes a larger electrostatic capacitance Csd between a pixel electrode and a corresponding signal wire, as compared to a structure in which a pixel electrode is away from a corresponding signal wire by a predetermined distance. Accordingly, a pixel electric potential becomes likely to be changed by a corresponding source signal in response to an increase in capacitance Csd. This leads to deterioration in display characteristic, and such deterioration is called shadowing.
In view of the circumstances, there has been proposed dot inversion driving. The dot inversion driving is a driving method for suppressing such a change in pixel electric potential as is caused by the capacitances Csd between the signal wires and the pixel electrodes. According to the dot inversion driving, a polarity of each source signal is inverted every gate line, and at the same time, a polarity of each signal is inversed every source line.
Employment of such dot inversion driving makes it possible to dramatically reduce the shadowing phenomenon, as compared to 1H line inversion driving, thus making it possible to improve the display quality of a liquid crystal display device. In particular, the shadowing phenomenon can be dramatically reduced by lessening a difference between a capacitance Csd1 and a capacitance Csd2 respectively corresponding to pixels adjacent to each other along a direction in which scanning wires extend.
On the other hand, however, the dot inversion driving causes an increase in transmittance difference due to variation among the capacitances Csd between the signal wires and the pixel electrodes. Such an increase leads to an increase in the likelihood of variation in width of overlaps between the signal wires and the pixel electrodes among blocks, i.e., block separation (display unevenness), because there may occur misalignment in a case where a photolithographic step is carried out in units of blocks.
The term “block” here means one of those regions in a display panel which are defined so that exposures are performed in the respective regions. Examples of an exposure method encompass: a method for carrying out a step-and-repeat exposure with use of one or more masks; a method for carrying out a scanning exposure more than once with use of one or more masks; and a method for carrying out scanning exposures in a plurality of blocks at a time with use of one or more masks.
In view of the circumstances, Patent Literature 2 proposes an active matrix liquid crystal display device capable of preventing such deterioration in display quality as is caused by capacitances Csd between signal electrodes and pixel electrodes, and at the same time, suppress such block separation (display unevenness) as is caused by variation among the capacitances Csd.
Patent Literature 2 illustrates, in FIG. 4, one example of such a configuration for suppressing the occurrence of display unevenness. According to this configuration, each signal wire has a bent portion in the vicinity of first and second pixel electrodes adjacent to each other. With the bent portion as a border, one part of the signal wire is covered with the first pixel electrode, and the other part of the signal wire is covered with the second electrode.
Such a configuration is believed to lessen differences in transmittance among the blocks, because even if there occurs a certain degree of misalignment between one block and another in a photolithographic step the configuration reduces variation among the capacitances Csd between the signal wires and the pixel electrodes, even with each pixel electrode shaped into a rectangle as has been the case conventionally.